A rotation transmission device is known which is capable of selectively permitting and prohibiting transmission of rotation from an input shaft to an output shaft, and which includes a two-way clutch, and an electromagnetic clutch for selectively engaging and disengaging the two-way clutch.
The rotation transmission device disclosed in JP Patent Publication 2012-149746A includes a control retainer and a rotary retainer mounted between an outer ring and an inner ring mounted inside the outer ring such that the pillars of the respective retainers circumferentially alternate with each other, opposed pairs of rollers, each pair being received in one of pockets defined between adjacent pillars of the retainers, and elastic members each received between a pair of the rollers and biasing the rollers away from each other to standby positions such that one of each pair of rollers becomes wedged between a cylindrical surface and a cam surface when the inner ring rotates in one direction, thereby transmitting the rotation of the inner ring to the outer ring.
This rotation transmission device further includes an electromagnetic clutch mounted on an input shaft on which is provided the inner ring, and configured such that when the electromagnet of the electromagnetic clutch is energized, the control retainer moves in the axial direction. As a result, the control retainer and the rotary retainer rotate relative to each other in the direction in which the circumferential widths of the pockets decrease due to the action of a torque cam, as a motion converting mechanism, disposed between opposed surfaces of a flange of the control retainer and a flange of the rotary retainer. As a result, the pillars of the respective retainers move the pairs of rollers to disengaged positions, thereby prohibiting transmission of rotation from the inner ring to the outer ring.
The electromagnetic clutch comprises an armature coupled to the control retainer, a rotor axially opposed to the armature, and the electromagnet, which is axially opposed to the rotor. The rotor includes an inner tubular portion press-fitted to and thus rotationally fixed to the input shaft.
The electromagnet includes an electromagnetic coil and a core supporting the electromagnetic coil and having one end thereof disposed between an outer tubular portion and the inner tubular portion, of the rotor. The other end portion of the core has its outer periphery supported by the radially inner surface of the housing, and a bearing mounted in the inner periphery of the other end portion of the core rotatably supports the input shaft.
This rotation transmission device is further configured such that when the electromagnet of the electromagnetic clutch is de-energized, the control retainer and the rotary retainer rotate relative to each other in the direction in which the circumferential widths of the pockets increase under the biasing force of the elastic members disposed between the respective opposed pairs of rollers, thereby moving the opposed pairs of rollers to the standby positions, where the rollers can be instantly wedged between the cylindrical surface and the cam surfaces. Thus, the rollers can scarcely move in the rotational direction, so that the rotation transmission device is quick in response.
With the rotation transmission device disclosed in JP Patent Publication 2012-149746A, since the rotor and the electromagnet are separately mounted on the input shaft, it is time-consuming to assemble this rotation transmission device.
Also, since the axial positioning arrangements for the rotor and the electromagnet are spaced apart from each other in the axial direction, the axial overlap distance tends to vary between the outer tubular portion of the rotor and the core of the electromagnet, which is mounted in the outer tubular portion, due to manufacturing and assembling errors. Thus, it is difficult to control this overlap distance, which in turn makes it impossible to stabilize the attraction force applied to the armature. It is therefore desired to make it easier to control the above-mentioned overlap distance.